The aim of the proposed research is an understanding of parainfluenza virus genome replication at a molecular level. The minus strand RNA genome of this class of viruses replicates not as free RNA but complexed with the viral N-protein in the form of the viral nucleocapsid. These viral nucleocapsids, containing genome RNA which is either plus or minus in sense, must contain recognition sites for the initiation of RNA synthesis by the viral replicase and for attachment of N-protein to the nascent RNA strand of the replicative intermediate to initiate the process of nucleocapsid assembly. Since these recognition sites are most likely to be situated at the ends of genome RNA, we proposed to sequence both ends of Sendai and NDV RNA in the hope that a comparison of the base sequences at the ends of Sendai and NDV RNA will help define these sites. Further experiments are proposed which hopefully will define those nucleotide sequences involved in recognition more precisely. We also propose to examine whether the ends of the genome RNA within the nucleocapsid are "sticking out" or complexed with N-protein so as to determine whether the viral replicase recognizes free RNA-N protein complex. In addition, we intend to develop an in vitro genome-RNA replication system in order to determine which viral, and possibly also host, proteins are involved in viral RNA replication.